On Wed, 3 Dec 2008 10:07:33 -0800 (PST), wrote:

- as would possibly a gravity circulated solid fuel stove.

Which are explicitly forbidden as a means of heating unvented HWCs.

That's why you do it with a pump...

Not relevant and bad practice with or without and unvented HWC. You simply
can't turn a solid fuel stove off like you can a gas or oil boiler. A
stove with a boiler must, under all circumstances including electricity
power failure, have some means of dumping the heat. Be that into a
heatstore or once that is hot a radiator as well.

--
Cheers
Dave.